FeSO47H2O is to be produced in a Swenson-Walker crystallizer by cooling a solution with 38% anhydrous FeSO4 (wet basis) from 310K to 300K. If cooling water enters and leaves the unit at 285K and 298K respectively (countercurrent) and 2% of initial water available in solution evaporates during the process, how many sections of crystallizer, each 5m long, will be required to process 1.25kg/s of the product